Gradient Mo Doping via Fick's Law for Stabilizing Lattice Oxygen in Lithium-Rich Manganese-Based Cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Solid-state Chemistry

Background:

• Lithium-rich (LR) manganese-based cathodes offer high energy density via oxygen redox.
• However, they suffer from structural degradation and poor cycling stability due to irreversible oxygen release.
• Stabilizing bulk lattice oxygen and surface interfaces is crucial for improving LR cathode performance.

Purpose of the Study:

• To develop a gradient molybdenum (Mo) doping strategy for stabilizing lithium-rich manganese-based cathodes.
• To investigate the effects of Mo doping on oxygen stability, structural integrity, and electrochemical performance.
• To provide a unified surface-to-bulk modification route for high-energy-density LR cathodes.

Main Methods:

• Fick's law-guided gradient Mo doping strategy.
• In situ formation of Li₂MoO₄ coating and partial spinel structure.
• Electrochemical performance testing (capacity, cycling stability) and theoretical calculations (Li⁺ diffusion barrier, oxygen stability).

Main Results:

• Gradient Mo doping effectively suppresses irreversible oxygen release.
• An in situ Li₂MoO₄ coating and partial spinel structure were formed, enhancing surface protection.
• The optimized LR@S-Mo cathode achieved a reversible capacity of 195.1 mAh·g^-1 with 88.6% retention after 300 cycles.
• Theoretical calculations confirmed reduced Li⁺ diffusion barriers and enhanced oxygen stability.

Conclusions:

• Gradient Mo doping provides a robust method for stabilizing lithium-rich manganese-based cathodes.
• The combined surface and bulk modification strategy significantly improves cycling stability and energy density.
• This approach offers a promising pathway for developing next-generation high-energy-density lithium-ion batteries.